[ros-release] doc jobs for dry repos require stack.xml

[Dirk Thomas]

We have recently discovered that several doc jobs for Fuerte and Groovy are marked as "unstable".
After investigating the source of the problem we identified that several repositories only contain dry packages but no dry stack.

Since stacks are the release unit in the dry world the package manifest does not provide enough information on dependencies on its own.
Therefore those repositories should contain a stack manifest as well.
Without that the necessary dependencies can not be installed (since they are specified in the stack.xml) and e.g. messages can not be generated and therefore also not be documented.

   One example job (just the first in alphabetical order) is http://jenkins.ros.org/view/Gdoc/job/doc-groovy-ar_kinect/
   The job can only find the package dependencies:
     """Dependencies: [u'visualization_msgs', u'artoolkit', u'ar_pose', u'geometry_msgs', u'tf', u'pcl_ros', u'opencv2', u'cv_bridge', u'roscpp', u'glut']"""
   A stack.xml file could provide the necessary stack-level dependencies which can otherwise not be resolved:
     """WARNING, could not find dependency artoolkit, not adding to list"""
     """WARNING, could not find dependency ar_pose, not adding to list"""

So if you are a maintainer of a repository which contains dry packages but no stack and get notification emails from Jenkins complaining that the doc job is "unstable" (with a yellow ball) you might 
want to consider to add a stack.xml to your source repository to allow the doc job to finish cleanly and document generated content.
With that change it will not only make the job turn "green" but also stop the continuous notification emails from appearing in your inbox...

- Dirk